Optical scanning head

ABSTRACT

The optical scanning head includes at least one trio of light emitting diodes arranged so the LEDs emit light at different angles to create a fan of light. An optical module includes a light shield or &#34;dark room&#34; and a lens/filter assembly which provides control of the depth of focus of the scanner. The optical module is located behind the light source, and the detector, made up of a CCD array is mounted behind the optic module for detecting the light intensity in the reflected beam over a field of view across a bar code symbol. The CCD array generates an electrical signal indicative of the detected light intensity. A DC source or battery provides DC voltage to the LEDs and CCDs in response to a clocked signal which provides a gradual or sequential illumination of the LEDs and coordinates the activation of the CCDs in order to minimize power consumption during scans.

This is a continuation of application Ser. No. 07/956,646, filed Oct. 2,1992, now U.S. Pat. No. 5,349,172 of application Ser. No. 07/843,266,filed Feb. 27, 1992, now U.S. Pat. No. 5,291,009.

FIELD OF THE INVENTION

The invention generally relates to a scanning system for reading and/oranalyzing bar code symbols and more particularly, to a portable bar codescanner.

BACKGROUND OF THE INVENTION

Many industries, including the assembly processing grocery and foodprocessing industries, utilize an identification system in which theproducts are marked with a bar code symbol consisting of a series oflines and spaces of varying widths. A number of different bar codereaders and laser scanning systems have been developed to decode thesymbol pattern to a multiple digit representation for inventory,production tracking, and for check out or sales purposes. Opticalscanners are available in a variety of configurations, some of which arebuilt into a fixed scanning station and others of which are portable.The portability of an optical scanning head provides a number ofadvantages, including the ability to inventory products on shelves andto track portable items such as files or small equipment. A number ofthese portable scanning heads incorporate laser diodes which permit theuser to scan the bar code symbols at variable distances from the surfaceon which the bar code is imprinted. A disadvantage of laser scanners isthat they are expensive to manufacture.

Another type of bar code scanner which can be incorporated into aportable system uses light emitting diodes (LED) as a light source andcharge couple devices (CCD) as detectors. This class of bar codescanners is generally known as "CCD scanners". While CCD scanners havethe advantage of being less expensive to manufacture, they limit theuser to scanning the bar code by either contacting the surface on whichthe bar code is imprinted or maintaining a distance of no more than oneand one-half inches away from the bar code, which creates a furtherlimitation in that it cannot read a bar code any longer than the windowor housing width of the scanning head. Thus, the CCD scanner does notprovide the comfort or versatility of the laser scanner which permitsvariable distance scanning of bar code symbols which may be wider thanthe window or housing width.

SUMMARY OF THE INVENTION

It is an advantage of the present invention to provide an opticalscanning head for reading bar code symbols at variable distances fromthe symbol which uses LED light sources and CCD detectors.

It is a further advantage of the present invention to provide a CCDscanner which permits measurement of bar code symbols which are greaterthan the window or housing width of the scanner.

In an exemplary embodiment, the optical scanning head comprises at leastone trio of light emitting diodes arranged in a generally "V" shapedconfiguration with each of the LEDs being oriented to emit light atdifferent angles so that a fan of light is created. The number of LEDscan be any multiple of three, up to twenty-four (24), i.e., from one toeight trios. The trios themselves can be grouped to form, for example,two sextets or one group of twelve. An optical module includes a lightshield or "dark room" and a lens/filter assembly which provides controlof the depth of focus of the scanner. The optical module is locatedbehind the light source, and the detector, made up of a CCD array ismounted behind the optic module for detecting the light intensity in thereflected beam over a field of view across a bar code symbol. The CCDarray generates an electrical signal indicative of the detected lightintensity. This signal is conveyed to a signal converter consisting ofan analog filter and analog-to-digital conversion circuitry to filternoise and digitize the analog signal to generate data descriptive of thebar code symbol. An automatic gain control is provided to adjust themagnitude of the received signal to a pre-determined level, regardlessof the distance between the bar code and the scanner. A lighttransmissive window is positioned in front of the LEDs. The window mayinclude a filter and/or anti-reflection coating.

In an alternate embodiment, a generally straight row of LEDs is providedto create a uniformly illuminated fan of light. The fan of light iscreated by orienting the LEDs at different angles, with the outer LEDsbeing angled more toward the outside.

The optical scanning head is powered by a D.C. source or battery,preferably rechargeable, which provides DC voltage to the LEDs and CCDsin response to a clocked signal which provides a gradual, serialillumination of the LEDs and coordinates the activation of the CCDs inorder to minimize power consumption during scans. Alternatively, thevoltage supplied to the LEDs can be modulated in response to the levelof the signal produced by the CCDs. If a bar code is scanned at closerange, a lower level of light will provide a strong signal. However, atgreater distances from the bar code, higher light intensity is necessaryto achieve a good quality signal at the CCDs. Power is conserved in thelatter version by not providing full power to the LEDs unless necessary.

BRIEF DESCRIPTION OF THE DRAWINGS

Understanding of the present invention will be facilitated byconsideration of the following detailed description of a preferredembodiment of the present invention, taken in conjunction with theaccompanying drawings, in which like reference numerals refer to likeparts and in which:

FIG. 1 is a diagrammatic view of the relative layout of the LEDs,optical module, and detector on a printed circuit board;

FIGS. 2a, 2b and 2c are diagrammatic views of relative locations of LEDsfor one trio, two trios and three trios of LEDs, respectively;

FIG. 3 is an exploded view of the lens assembly;

FIG. 4 is a perspective view of an assembled optical scanning headincluding a housing;

FIG. 5 is a cross-sectional view along line 5--5 of FIG. 4;

FIG. 6 is a circuit diagram of the LED board for the 12 LEDconfiguration of FIG. 1;

FIGS. 7a through 7g are plots of clock pulses for different timingconfigurations with respect to activation of the scanner (FIG. 7a);alternate illumination cycles (FIGS. 7b, 7c and 7d) according to thepresent invention; analog reset of the detector (FIG. 7e); andillumination patterns according to prior art methods 1 and 2 (FIGS. 7fand 7g);

FIG. 8 is a block diagram of the operational sequence of the opticalscanning head according to the present invention;

FIG. 9 is a diagrammatic view of an alternate LED layout and thecorresponding light distribution;

FIG. 10 is a diagrammatic view of a second alternate LED layout and itscorresponding light distribution;

FIG. 11 is a diagrammatic view of a third alternate LED layout and itscorresponding light distribution; and

FIG. 12 is a block diagram of the scanning sequence.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The scanning head module illustrated in FIG. 1 comprises the printedcircuit board (PCB) 2 configured as a generally "U"- or "Y"-shapedsurface onto which is mounted one or more trios of LEDs (from 3 to 24individual LEDs) configured in a generally V-shaped pattern in anorientation that results in projection of a light ray by one LED in adirection distinct from other LEDs in the trio. The configurationillustrated in FIG. 1 has 12 LEDs identified as LEDs 4 through 15, whichemanate rays of light 104 through 115. The portion of printed circuitboard 2 from which LED light emanates will be considered the front ofthe board. At the approximate center of board, behind the LEDs, anoptical module 17 consisting of a light shield (dark room 16), in whichis contained lens assembly 18 which filters and focuses light reflectedfrom a scanned bar code onto CCD detector 20, disposed behind theoptical module at the rear of PCB 2. A signal generated by activation ofthe CCDs by the reflected light generates a signal which is conveyed tosignal converter 22 which consists of an analog filter and ananalog-to-digital circuit. Forward of the LEDs, either attached to thePCB 2 or mounted within a housing containing PCB 2, is window 24 whichis light transmissive and provides filtering and positioning of thelight path of the illuminating beam incident upon the bar code to bescanned then transmits the reflected light carrying the intensitymodulated bar code signal back to the lens assembly and to the detector.

The scanning head may also include a decoder module 26 which decodes amultiple-digit representation of bar code symbols such as UPC, EAN, JAN,Code 39, Code 2/5I, Code 2/5, Code 128, Codabar, Plessey, and other barcode systems.

The light source consisting of the trios of LEDs is illustrated in FIG.1 as possessing 12 LEDs which are mounted in a generally V-shapedconfiguration relative to other LEDs so that they point outward atangles such that groupings of three on a single leg, e.g. LEDs 4, 5 and6 or 13, 14 and 15 form substantially a single beam of light whichexpands at increased field depth. The actual grouping of the trios ofLEDs is best illustrated in FIGS. 2a, b and c. From this it can be seenthat the trios of LEDs are not determined by serial progression of theirlocation in the V-configuration, but rather that the combinedillumination of the trio substantially fills the window 24 and expandstherefrom to form a fan of light to facilitate detection of bar codeswhich are wider than the window itself.

In FIG. 2a, LEDs 6,10 and 13 make up the first trio. Light rays 106, 110and 113, shown in FIG. 1, fill a substantial portion of the window 24.The second trio of LEDs comprises LED 5, LED 10 and LED 14, which areadded to the first trio, as shown in FIG. 2b. The beams emanatingtherefrom, rays 105, 110 and 114, shown in FIG. 1, supplement rays fromthe first trio to fill window 24 and expand therefrom. FIG. 2cillustrates the location of the third trio consisting of LEDs 7, 11 and12. Rays 107, 111 and 112 emanate therefrom to supplement the light fromthe first two trios. The fourth trio is made up of LEDs 4, 8 and 15 withtheir respective rays 104, 108 and 115. The specific LEDs includedwithin a given trio are variable as long as the resultant fan of lightsubstantially fills the window 24. As will be described below, thedesignated trios may be sequentially illuminated in order to conservethe energy of the power source. The configuration having twelve LEDs canalso be divided into two sextets, in which two trios are combined ineach sextet. Similarly, if 24 LEDs are used, the groupings can be inmultiples of six or twelve. The grouping of the LEDs is significant whensequential or graduated illumination is used.

An alternate configuration for arrangement of the LEDs is a generallystraight line across the front of the board, as illustrated in FIG. 11.The fan of light is created by orienting the LEDs at different angles.In the straight line configuration, the centermost LEDs 209 and 210, areturned to point away at an angle of 1.625 degrees from a line normal tothe front of the board. Progressing outward, each LED is 3.25 degreesfrom its inner adjacent LED.

The LEDs are selected so that they emit light at the wavelength of 660nanometer, red light within the visible spectrum. This wavelengthprovides optimal contrast for bar code scanning applications in whichdark and light bars must be distinguished. Infrared light also providesenhanced contrast, so that LEDs emitting light outside of the visiblespectrum may be used.

The optic module 17 consists of three lenses mounted inside a slidablelens support 30, all of which are retained within dark room 16. Theselection of the three lenses of which the lens assembly 18 is formeddepends upon the desired reference plane, i.e., the desired depth offield, which is the distance between the detector 20 and the bar codebeing scanned, so the reflected light is appropriately focused on thedetector array. The lens assembly 18 consists of a plano-convex lens 32followed by a bandpass filter 34, a biconcave lens 36 followed by anoptical diffuser 28 and a focussing and receiving singlet lens 40. Inthe prototype model, the lens focal lengths were selected to be 10.69 mmfor lens 32 and 7.49 mm. Lens 40 is important to the success of theinvention since it determines the beam diameter impinging upon thedetector array, and concentrates the beam to provide the maximumavailable light. In the prototype device, the forward focal length oflens 40 was 18.68 mm, and the back focal length was 16.68 mm. The lensesmay be coated with an anti-reflection coating and/or a pass-band coatingto minimize reflectance at the interfaces between the adjacent lensesand at the ends of the lens assembly.

The optimum depth of field can be adjusted by moving the lens assemblyforward or backward in its slidable mounting 21 with respect to thedetector. This will modify the focal point on the detector so that itcan be fine tuned for a desired scanning height.

A spatial filter may be included within the optical module, disposedadjacent to or even integral with the lens assembly 18. The spatialfilter 42 is an air slit with an orientation and configurationcorresponding to the shape of the bar code being scanned. Specifically,the slit is oriented vertically so that it is parallel to vertical barsof the bar code and has dimensions on the order of 5 millimeters high byone millimeter wide. The light absorber/diffuser 28 is in the form of afunnel having an aperture on the order of 4.5 millimeters with its widerend facing towards the detector end of the lens assembly. The funnelallows absorption and concentration of light diffracted from the edgesof the lenses. The bandpass filter 34 serves to block any radiationwhich falls outside of a wavelength range centered around 660 nm (orwavelengths surrounding infrared light for the infrared scanner). Forthe visible light system, it is particularly desirable to filter theinfrared and other visible portions of the light spectrum which mayreach the window from the sensing region to provide optimal contrast.This improves resolution of bar codes read at a distance shorter thanthe depth of field.

The window 24 consists of a bandpass filter centered at approximately660 nm (for the visible light scanner) and a light equalizer/diffuser,and may be combined with, or separate from, a cylindrical lens 38, whichfocuses the light along one axis to form a plane of light, with a lineof light being created at its focal point, which is approximately 7inches. When the bar code is scanned at the precise focal point of thecylindrical lens 38, the maximum possible light will be reflected to thedetector. The window's function is to suppress radiation noise from theLEDs, to form a homogeneous incident beam for illumination of the barcode, to collimate the beam, and to filter the reflected light byremoving extraneous light which falls outside of the predeterminedacceptable bandwidth range of 660 nm.

The detector 20 consists of an array of charged coupled devices (CCD)which are arranged in equally spaced pixels. The spacing of the pixelsdetermines the limit of the resolution of the detector, so it isnecessary to match the CCD resolution to the required spatial resolutionin the image plane in which the detector lies. The magnification of thelens system should be chosen so that at least 2 CCD pixels cover theminimum bar width to be resolved in the image plane. This is especiallyimportant for bar codes printed with a dot matrix printer.

Electrical power is provided to the CCD array by D.C. source or battery46. In a first embodiment of the invention, the supply of power to theCCD array is coordinated by a clocking signal with the sequential orgraduated illumination of the LEDs. Specifically, as seen in FIG. 7e, aclock signal (from clock 50) is provided to the CCD array to clear it incoordination with the activation of the LEDs. The CCD array can bescanned at a variable rate, from 36 to 200 scans per second, with therate being determined by the density of the bar codes being scanned. Thescan rate is set by the system clock which then modifies theillumination sequence of the LEDs so that the coordination illustratedin FIGS. 7a-7e will be maintained. The determination of scan rate can bepreprogrammed and can be initiated by scanning a bar code with thescanning rate set-up information, or other relevant information, priorto measurement of the bar codes of interest.

The processing sequences are shown in FIGS. 8 and 12. The signalprovided by the CCD array will be amplified then processed through a lowpass two pole filter and a high pass (25 KHz-30 KHz) five pole filter(shown combined as filter 52) which will extract the useful signal anynoise generated either by the incoming light or by the CCD array itself.An optional automatic gain control (AGC) 54 will adjust the level of thesignal to a pre-determined level. The level of the signal entering theAGC is a function of the distance at which the bar code is scanned. Thegreater the distance that the scanner is held above the scanned code,the weaker the signal will be. A filtered signal will then provide avoltage to a circuit which determines the real time center point ("zerocrossing") reference level to a comparator with a gain of 500,000 whichwill convert the analog video output signal to a digital signalrepresenting the bar code. The use of an automatic comparator control(ACC) 56 will avoid noise generated by hysteresis and will avoid missingthe white guard and the first commutation which represents the first barin the video signal. The signal is then converted from analog to digitalby A/D converter 58 and sent to decoder 26.

In an alternate embodiment, rather than sequentially illuminating theLEDs, the voltage to the LEDs is regulated in response to the signallevel in the detector. The stronger the received signal, the lower theintensity of light required from the LEDs. The strength of the signal isdependent upon the distance between the scanner and the bar code, so, atthe maximum scanning distance, the LEDs will receive full power. Thisconserves power by only demanding the power that is necessary. It alsoavoids saturating or distorting the detected signal if the bar code isread at a short distance from the scanner with high intensity light.

The optical scanning head of the present invention provides forconservation of power supply energy by using a system clock to control ascanned, progressive illumination of the LEDs in coordination withclearing of the CCD array. The circuit diagram in FIG. 6 is provided toillustrate the sequential control of the four different LED trios whichare illustrated in the embodiment of FIG. 1. For example, the clockdriver provides a signal to activate amplifier U2A which then provides asignal to the first trio, identified as TRIO 1, to illuminate LEDs 5, 6and 12. TRIO 1 is connected so that it will be on at all times that thescanner is activated, regardless of which other trios are on (note thebase-collector short at transistor QS).

FIG. 7 provides samples of pulse patterns for activation of the LEDs ofthe embodiment illustrated in FIG. 1. FIG. 7a illustrates the activationof the scanner at the beginning of a first clock pulse, i.e., the poweris turned on. According to the pulse pattern illustrated in FIG. 7b uponapplication of the "turn on" signal, first trio of LEDs (TRIO 1) isilluminated. At the beginning of the second clock cycle a second trio(TRIO 2) is illuminated. Also at this time, a signal is provided to theCCD array to reset it to initiate its detection function, shown in FIG.7e. At the beginning of the third clock cycle a third trio of LEDs (TRIO3) turns on, and during a fourth clock cycle a fourth set of LEDs (TRIO4) turns on. During the fifth clock cycle TRIO 2, TRIO 3 and TRIO 4 turnoff and only TRIO remains on. This step up/drop down sequence iscontinued until the trigger is turned off at the point illustrated inFIG. 7a. In FIG. 7c a second possible pulse pattern is illustrated inwhich the first trio of LEDs turns on during the first clock cycle and asecond LED trio turns on the second clock cycle, then turns off in thethird clock cycle so that the first trio remains on until the seventhclock cycle when the second and third trios turn on for a single clockcycle. The first trio of LEDs remains on during the entire procedure andin the twelfth clock cycle, all four trios of LEDs turn on for onecycle. After a single clock cycle, where only the first set of LEDsremain on, the sequence repeats. In FIG. 7d the pulse pattern alternatesbetween two trios of LEDs being on and turning on four trios of LEDs,with one trio being on at all times. For comparison of the inventivemethod to prior art practices, FIGS. 7f and 7g are provided. In FIG. 7f,a simple alternation occurs between on and off. In FIG. 7g, anycombination of the LEDs remains on at all times that the trigger isactivated.

In an alternate embodiment, power conservation is achieved by regulatingthe voltage supplied to the LEDs in response to the level of the signalgenerated by the detector array. As above, the detector signal level isdependent upon the distance at which the bar code is scanned. Forgreater distances, the signal level will be lower. In response to thislower signal, the voltage supplied to the LEDs will be increased. Whenthe signal level is above a pre-determined limit, the voltage suppliedto the LEDs will be less, since less light is needed to provide anacceptable signal. As an example, if the bar code is read at closerange, the LEDs will be supplied with a 25% of the maximum currentdrain, which, in the prototype device, is 5 mA. If the bar code is readwithin the middle of the total field depth, the LEDs receive 50%, or 10mA. At the outer limits of the field depth, the supplied current will be20 mA. The percentage of power applied to the LEDs may change with thecolor of the bar code as needed to obtain the optimal light intensityfor scanning. This power management technique will use the level of thevideo output signal to command and control the current on the LEDsthrough an appropriate clocking function

The light path of the incident beam at the front region of the scannerwill generate a beam of light through angular distance over a field ofview across the bar code symbol located in the vicinity of the referenceplane. The width of the light transmissive window 24 represents alimiting factor for the width of the incident beam. For this reason, theLEDs are mounted as close as possible to the window 24 to optimize thefield of view and the incident beam power. Despite this limitation, thefield of view of the incident beam is generally independent of the widthof the PCB 2 or of the housing. This permits the field of view, i.e.,the transverse beam dimension of the incident beam to be larger than thewidth of the window 24. This is due to the fact that the LEDs emit theincident beam at different directions from each side of the devicewithin the scanning head. The LEDs are oriented to provide parallelbeams in pairs. For example, a first pair of LEDs, LEDs 4 and 7 areoriented at a 7.5° angle on the y-axis (a line normal to the front ofthe PCB 2), 5 and 8 are oriented at 15°, and LEDs 6 and 7 are orientedat 22.5°, as illustrated in FIG. 9. The LEDs on the other leg of the "V"are similarly oriented in the opposite direction. As can be seen in thefigure, the fan of light which results from this orientation provides anintensity distribution which is higher within a narrow region at thecenter of the fan, as determined at a distance of 7 inches from thescanner.

The alternate LED arrangement shown in FIG. 10 places the centermostLEDs at an angle of 3.75 degrees from a line normal to the front of thescanner, with the other LEDs being oriented at 3.75 degree increments asthey progress outward along the legs of the "V". This LED configurationresults in a slightly wider region of higher intensity as compared tothe above-described embodiment.

A third configuration of the LEDs is illustrated in FIG. 11, which showsa line of LEDs at varying orientations. This configuration is describedabove.

Other electrical sub circuits can also be provided on PCB 2, includingthe analog filter 52 and a/d converter 58. However, in order toconfigure the housing of the scanner in desired position, it may benecessary to provide a second circuit board oriented at some angle tothe first circuit board onto which additional subcircuits can be placedincluding a decoder chip and a memory device. For example, two circuitboards can be configured so that one abuts the other at approximateright angles to create an "L"-shaped arrangement. This arrangement wouldallow placement of one of the boards in the barrel of a scanning gunwith the other board extending partially into the handle portion.

The decoder module 26 may be either inside or outside of the scanninghead housing and will process the digitalized signal generated in thescanning head to calculate the desired data, e.g., the multiple digitrepresentation or code represented by the bar code symbol in accordancewith the algorithm contained in the software program. The decoder moduleincludes a random access memory (RAM) for temporary data storage, andEPROM or PAL for holding the control program and a microprocessor whichcontrols the RAM and EPROM or PAL. The decoder module will also includecircuitry for controlling the scanning head and the communicationcircuitry for communication with different functions of the scanninghead or with a host system to which the scanning head can be connected,such as a hand held terminal data screen personal computer for computernetwork.

A low battery detector 60 is included in the housing to provide anindication of insufficient power for further scans. This will provideadvance warning so that the user will be aware of the problem beforehaving scanned a number of items without realizing that the items cannotregister properly due to the insufficient power.

The circuitry, with or without the power supply of a portableconfiguration, of the optical scanner is protected within a housing 30which is contoured to easily fit into the user's hand. The user willgrip the housing 30 by its handle portion 32, illustrated in FIGS. 4 and5, with the window portion 34 aimed at the bar code symbol to be read.The trigger 36 is built within the handle 32 for easy, one-handedoperation of the scanner, with the trigger being positioned at a shortdistance from the user's fingers so that activation is simply a matterof depressing the trigger. The window portion can be placed anywherefrom 0 to 22 inches above or in front of the bar code to be scanned.With a scanning distance of less than seven inches, it is desirable tocenter the fan of light over the bar code since different brightnessesdue to the sequential limitation of the LEDs may illuminate someportions of the bar code more brightly than others, and due to thehigher density of light at the center of the fan.

The optical scanning head of the present invention provides a device forbuilding a small or self-contained portable device, a portable componentof a multi-component scanner, or the optical portion of a built-inscanning unit, for bar code scanning which uses LED and CCD technologymaking it an economical device. The scanning head is capable of readingbar codes up to 22 inches away from the detector so that it is versatilefor either portable or fixed implementation. The variably pulsedactivation of the LEDs and CCD array, or the graduated illumination ofthe LEDs, makes the device capable of operating at low power withminimal power drain during illumination, a significant factor inportable scanners. The lens system and fan of light produced by the LEDarray permit the reading of wide range of bar code densities and widths.

It will be evident that there are additional embodiments which are notillustrated above but which are clearly within the scope and spirit ofthe present invention. The above description and drawings are thereforeintended to be exemplary only and the scope of the invention is to belimited solely by the appended claims.

I claim:
 1. An optical scanner for reading and decoding informationencoded in a bar code comprising alternating lines of light and dark,said optical scanner comprising:a printed circuit board having a front,a center and a rear; an array of light emitting diodes comprising atleast one combination of light emitting diodes disposed at said front ofsaid printed circuit board in an arrangement wherein each light emittingdiode of said at least one combination emits light at a non-zero anglewith respect to a centerline bisecting said printed circuit board fromsaid front to said rear so that a fan of light is projected from saidarray toward a reference plane within a field of view containing saidbar code so that light is reflected therefrom; an optical assemblydisposed at a center of said printed circuit board for receiving,concentrating and directing reflected light toward said rear of saidboard; a CCD array disposed at said rear of said printed circuit boardfor detecting a portion of said reflected light directed thereon by saidoptical assembly and generating an electrical signal in response theretowherein said electrical signal is an analog representation of said barcode; a conversion assembly for receiving and converting said electricalsignal into a digital signal corresponding to said bar code; and avoltage source for providing a driving voltage to said array of lightemitting diodes, said CCD array and said conversion assembly.
 2. Anoptical scanner as in claim 1 wherein said array of light emittingdiodes comprises at least two combinations of light emitting diodes andfurther comprising:a clocking device for controlling a transfer ofdriving voltage from said voltage source to each combination of lightemitting diodes wherein a first said combination remains on when saidoptical scanner is activated and at least one second said combination isperiodically turned on and off according to a clocking signal generatedby said clocking device.
 3. An optical scanner as in claim 1 furthercomprising:a clocking device for controlling transfer of driving voltagefrom said voltage source to said at least one combination of lightemitting diodes; and a gain controller responsive to a level of saidelectrical signal for controlling a level of driving voltage applied tosaid at least one combination of light emitting diodes.
 4. An opticalscanner device as in claim 3 wherein said gain controller ramps up saidlevel of said driving voltage when said optical scanner is at a greaterdistance from said bar code.
 5. An optical scanner as in claim 1 whereinsaid field of view has a depth in the range of 0 to 22 inches.
 6. Anoptical scanner as in claim 1 wherein said array of light emitting diodeis disposed in a generally V-shaped arrangement.
 7. An optical scanneras in claim 1 wherein said array of light emitting diodes is disposed ina generally straight row across said front of said printed circuitboard.
 8. An optical scanner as in claim 1 wherein said optical assemblycomprises a plurality of lenses and filters for optimizing saidreflected light for detection by said CCD array.
 9. An optical scanneras in claim 1 wherein each light emitting diode of said array emitsvisible red light.
 10. An optical scanner as in claim 9 wherein saidvisible red light has a wavelength of 660 nanometers.
 11. An opticalscanner as in claim 1 wherein each light emitting diode of said arrayemits infrared light.
 12. An optical scanner as in claim 8 wherein saidoptical assembly includes a bandpass filter for blocking light having awavelength outside of a range around a pre-determined wavelength atwhich said array of light emitting diodes emits.
 13. An optical scanneras in claim 1 further comprising a window disposed at said front of saidprinted circuit board for filtering said fan of light and said reflectedlight.
 14. An optical scanner as in claim 1 wherein said conversionassembly includes an automatic gain control for controlling gain inresponse to a detected intensity level of said reflected light.
 15. Anoptical scanner as in claim 2 wherein said clocking device furthercontrols a timing of scanning of said CCD array and a transfer of saidelectrical signal to said conversion assembly.
 16. An optical scanner asin claim 1 wherein said optical assembly further comprises a lightshield to block out stray light.
 17. An optical scanner as in claim 1wherein said optical assembly is slidable in a direction running fromsaid front to said rear of said printed circuit board to permitvariation in a depth of field of said optical scanner.
 18. An opticalscanner as in claim 1 wherein said CCD array has a density of elementsselected according to a density of said alternating lines of said barcode.
 19. An optical scanner as in claim 1 wherein said fan of light hasan intensity distribution which is denser at a center of said fan. 20.An optical scanner as in claim 1 further comprising a housing forhand-held operation.
 21. An optical scanner as in claim 20 furthercomprising a trigger for activating and de-activating said opticalscanner.
 22. An optical scanner as in claim 1 further comprising meansfor indicating a drain of said voltage source.
 23. An optical scanner asin claim 1 further comprising a cylindrical lens disposed in front ofsaid array of light emitting diodes for creating a line of light at afocal point of said cylindrical lens.
 24. An optical scanner forscanning a bar code symbol having a first width, said optical scannercomprising:at least one printed circuit board having a front, a center,a rear and a longitudinal centerline bisecting said at least one printedcircuit board into a first side and a second side, said front having asecond width smaller than said first width; a plurality of LEDs disposedon said front of said at least one printed circuit board for emitting anincident beam of light for illuminating said bar code symbol, a firstportion of said plurality of LEDs being disposed on said first side anda second portion of said plurality of LEDs being disposed on said secondside, each of said first portion and said second portion of LEDs beingoriented to emit light at a non-zero angle with respect to saidcenterline so that a first half of said incident beam emitted by saidfirst portion of LEDs intersects a second half of said incident beamemitted by said second portion of LEDs wherein said incident beam oflight has a beam width which increases at increasing distances from saidfront of said at least one printed circuit board; an optical focusingmeans disposed at said center of said at least one printed circuit boardfor focusing light; a detector means disposed at said rear of said atleast one printed circuit board for detecting light focussed by saidoptical focussing means and generating an electrical signalrepresentative of said bar code symbol therefrom; a signal processingmeans in electrical communication with said detector means forconverting said electrical signal into an output comprising datadescriptive of said bar code symbol; and a voltage source for providingvoltage to said plurality of LEDs, said detector means and said signalprocessing means.
 25. An optical scanner for scanning a bar code symbolhaving a first width, said optical scanner comprising:a housing forhand-held operation having a second width at a front end at which anincident beam of light for illuminating said bar code symbol exits saidhousing, said second width being smaller than said first width, saidhousing having a handle portion having dimensions for being held in auser's hand; at least one printed circuit board retained within saidhousing and having a front corresponding to said front end of saidhousing, a center, a rear and a longitudinal centerline bisecting saidprinted circuit board into a first side and a second side; a pluralityof LEDs disposed on said front of said at least one printed circuitboard, a first portion of said plurality of LEDs being disposed on saidfirst side and a second portion of said plurality of LEDs being disposedon said second side, said first portion of LEDs and said second portionof LEDs being positioned on either side of said centerline so that saidplurality of LEDs emits a diverging incident beam of light beyond saidfront end; an optical focusing means disposed at said center of said atleast one printed circuit board for focusing light; a detector meansdisposed at said rear of said at least one printed circuit board fordetecting light focused by said optical focusing means and generating anelectrical signal representative of said bar code symbol therefrom; asignal processing means for converting said electrical signal into anoutput comprising data representative of said bar code symbol; and avoltage source for providing voltage to said plurality of LEDs, saiddetector means and said signal processing means; wherein said opticalscanner is held at a distance from said bar code symbol and saiddiverging incident beam of light has a width at least as wide as saidfirst width at a point at which said diverging incident beam of lightcontacts said bar code symbol.
 26. An optical scanner as in claim 25further comprising a trigger disposed on said housing adjacent saidhandle portion for activating and deactivating said optical scanner.